ACPI: Remove side effect of partly creating a node in acpi_get_node()

acpi_get_node() calls acpi_get_pxm() to evaluate the _PXM AML method
for entries found in DSDT/SSDT. ACPI 6.3 sec 6.2.14 states
"_PXM evaluates to an integer that identifies a device as belonging to
 a Proximity Domain defined in the System Resource Affinity Table (SRAT)."
Hence a _PXM method should not result in creation of a new NUMA node.

Before this patch, _PXM could result in partial instantiation of
NUMA node, missing elements such as zone lists.  A call to
devm_kzalloc(), for example, results in a NULL pointer dereference.

This patch therefore replaces the acpi_map_pxm_to_node() with a call
to pxm_to_node().

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>